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The aim of this study was to evaluate different replacement levels of fishmeal ( FM) by feather meal (FeM) on survival and growth of juvenile crayfish ( Pacifastacus leniusculus). An 80-day experiment was conducted with stage 2 juveniles from the onset of exogenous feeding. Four practical diets (500 g kg−1 protein) differing in the level of replacement of FM protein by FeM protein were prepared: 0% (control diet), 15% (8.2% dietary FeM), 25% (13.7% dietary FeM) or 35% (19.2% dietary FeM). Each diet was tested on grouped or individually isolated crayfish. Crayfish fed the control diet or 15% replacement achieved the highest survival (average of grouped and isolated: 88.2%) and growth (grouped and isolated: 13.58 mm carapace length, 523.2 mg weight) and the lowest feed conversion ratio (average of grouped and isolated: 1.11). Final growth of isolated crayfish was significantly higher than that of grouped crayfish for all diets. This study provides the first data on the substitution possibilities of FM by FeM in diets for freshwater crayfish. An 8.2% of FeM (15% replacement of FM protein) can be included in extruded diets for juvenile P. leniusculus during the first 80 days of intensive rearing without impairing growth or feed conversion. [ABSTRACT FROM AUTHOR]

Branchiobdellidans or crayfish worms are clitellate annelids and ectosymbionts of freshwater crayfish. An investigation of branchiobdellidan infestation was undertaken in a population of endangered white-clawed crayfish (Austropotamobius pallipes) in the river Aire, UK. Thirty two percent of animals were infested either by the adult parasite or their cocoons (n=107). Parasite burden increased with host size, but did not differ with sex. Observations of crayfish gill tissue revealed a strong positive relationship between melanization of filaments and parasite prevalence and burden. Taxonomic identification revealed that 1 species of branchiobdellidan was present, Branchiobdella astaci. The first sequences were generated for this species and phylogenetically analysed alongside published sequences for 5 other branchiobdellidan species in Europe. The position of B. astaci within the genus Branchiobdella was confirmed, and it was found to cluster as a sister group to B. parasita. [ABSTRACT FROM AUTHOR]

We describe an intersex specimen of the Marmorkrebs, the oniy obligate parthenogenetic freshwater crayfish with an all-female population. The individual was a fully functional female which possessed male-like first pleopods. Nevertheless, it reproduced successfully and the offspring were normally developed parthenogenetic females, lacking any trace of male traits. The general rarity of aberrant sexual traits in freshwater crayfishes, in particular in Procambarus, is discussed. We suggest that a dysfunction of the sex determining system, which controls the anlagen of the androgenic glands during development, caused the partial male-like phenotype of this Marmorkrebs specimen. The application of this organism for investigations of sex determination and differentiation is recommended. [ABSTRACT FROM AUTHOR]

Austropotamobius pallipes is a vulnerable crayfish, and therefore it is necessary to analyse reproduction in the extant populations. Details of the female annual reproductive cycle in a Mediterranean population are provided for two consecutive years. Maternal-size-related variables and date of collection have been considered in relation to the number of ovarian and pleopodal eggs. Reproductive data from 2587 females collected by hand and traps are reported. In total, 204 (14.69%) and 231 (15.93%) individuals in 2003 and 2004, respectively, were ovigerous. Demonstrable differences exist between ovarian and pleopodal egg counts. In particular, ovarian egg counts were considerably higher than expected pleopodal egg numbers. Mating begins in November and is followed by egg laying in early December-January. Berried females occur until May-June, when hatching occurs. The numbers of both ovarian and pleopodal eggs are correlated with the size of females, although fecundity slightly decreases in larger females. The histology of the reproductive organs of both sexes is also analysed. [ABSTRACT FROM AUTHOR]

In present paper the results from a study on the Stone crayfish in the Dospat Dam were represented. During the study period a total of 551 stone crayfish were caught (328 males and 223 females) by traps. The size-weight characteristics of the population were established, as well as the determination of its relative density (CPUE), and the ratio between the males and the females. [ABSTRACT FROM AUTHOR]

This study observed agonistic interactions and contests between size-matched form I vs. form I, form II vs. form II, and form I vs. form II males to establish baseline dominance orders and behavioral dynamics for Procambarus suttkusi (Choctawhatchee Crayfish). Three types of initiation behaviors, or attacks, were observed during each interaction: ambivalent contact, claw raise, and lunge. Feeding competition studies were also performed to assess the relationship between the winners of the agonistic interactions and feeding contests. Only form I vs. form I contests showed a decline in the number of interactions observed over time, but the duration of each individual agonistic interaction declined for all three types of behaviors during the thirty-minute recording period. Winners and losers did not preferentially use the same initiation behaviors as used in other studies. Previous studies also documented form I dominating form II males, but form I males did not dominate form II males in the present study. Winners of the agonistic contests won significantly more feeding contests. The results of the current study suggested that behavioral dynamics and form dominance may be species specific and that careful consideration of size differences are necessary in order to examine form dominance. [ABSTRACT FROM AUTHOR]

Orconectes williamsi (Williams' Crayfish) is a rare stream-dwelling crayfish that is endemic to the upper White River basin of Arkansas and Missouri. It was described in the 1960s from a type locality in Madison County, AR, and the three localities named in the description comprise the published range of the species in Arkansas. In contrast, 27 locations have been reported in Missouri. This study surveyed a semi-random selection of stream sites in the Arkansas portion of this range in order to characterize the crayfish communities and evaluate the status of O. williamsi in Arkansas. A total of 2372 crayfishes were collected at 68 sites, including 197 Williams' Crayfish from 23 sites. Orconectes meeki meeki (Meek's Crayfish) was the crayfish species most commonly associated with O. williamsi, occurring sympatrically at 87% of sites occupied by O. williamsi. Orconectes williamsi was found in small streams, with coarse substrates and no aquatic vegetation. Orconectes williamsi showed a strong preference for riffle habitats. Due to its limited range and habitat requirements, O. williamsi is moderately imperiled in Arkansas and should be considered rare and vulnerable range-wide. [ABSTRACT FROM AUTHOR]

Introductions of nonnative crayfish species have resulted in the global decline of native crayfish populations, including those in North America. Historically, the North American range of Orconectes limosus (Spinycheek Crayfish) extended from Maine, southward into northern Virginia, including West Virginia's eastern panhandle. A 1988-1989 survey of the eastern panhandle of West Virginia resulted in the capture of only 14 O. limosus, but an abundance of the nonnative Orconectes virilis (Virile Crayfish). These data along with additional unpublished accounts of declines of O. limosus populations prompted our survey of eastern West Virginia. In 2005 and 2006, crayfishes were collected from streams within the West Virginia range of the O. limosus, including historic capture locations. Our collection of 600 individuals comprised crayfishes from 3 species: O. virilis, Orconectes obscurus (Allegheny Crayfish), and Cambarus bartonii bartonii (Common Crayfish). The nonnative O. virilis was present at 26 of the 30 sites, whereas O. limosus was absent from all collections. Our results may indicate extirpation of some or all populations of O. limosus in eastern West Virginia, but absence data may also reflect a low detection probability of individuals from small populations. Competition between the nonnative O. virilis and O. limosus have been reported elsewhere, and likely explains the extirpation of populations of O. limosus in West Virginia. [ABSTRACT FROM AUTHOR]

A key for the 3 crayfish species of the family Astacidae (Crustacea, Decapoda) found in Bulgaria: Astacus leptodactylus Eschscholtz, 1823; Astacus astacus (Linnaeus, 1758) and Austropotamobius torrentium (Schrank, 1803) is presented. More important identification characters are illustrated with original photographs. [ABSTRACT FROM AUTHOR]

The present study was carried out to evaluate the effects of selectivity of fyke-nets of different mesh size on Astacus leptodactylus (Eschscholtz, 1823), in lake Eğirdir in Turkey. Crayfish were sampled monthly using fyke-nets of 26 mm (control), 34 mm (traditional), and 42 mm (increased) mesh size from July to December 2007. Differences in the mean size, weight, and number of crayfish caught with each mesh size were determined. The average length and weight were found to increase proportionally to mesh size. The highest mean weight (g) (± SD) (41.07 ± 4.61) was achieved at 42 mm mesh size compared with mean weights of 32.76 ± 4.53 and 29.29 ± 4.37 at sizes of 34 and 26 mm, respectively. The same trend was observed in mean TL of crayfish caught at 42, 34, and 26 mm size, but no significant difference was detected in mean length and weight for male and female crayfish. The weight of crayfish caught in 42 mm mesh was 8.3% higher than that in 34 mm mesh size. The lowest number of crayfish was caught with the 42 mm mesh size, while the highest number was captured with 34 mm mesh. This study shows that increasing mesh size has a positive effect on selectivity, because the mean total length L50 in the catch approximates the minimum landing size for this species in Turkey. L50 values (total length) for female, male, and combined sexes were 9.93 ± 0.41 cm, 9.73 ± 0.34, and 9.93 ± 0.34 cm for 42 mm, and 6.54 ± 0.60 cm, 7.28 ± 0.30, and 7.09 ± 0.3 cm for 34 mm, respectively. It was presumed that 34 mm mesh size, which is commercially used, has poor selectivity. On the other hand, 34 mm mesh size caused a loss in marketable crayfish among the three tested mesh sizes. The 42 mm mesh size provided the most appropriate selection of the crayfish, compared with sizes of crayfish at 34, and 26 mm mesh, respectively. Meanwhile, as mesh size increases, the female escape ratio becomes higher than the male escape ratio. Thus, increase in mesh size of nets will have a positive impact not only on preserving a sustainable stock, but also sparing labour and time to be spent on fishing operations. [ABSTRACT FROM AUTHOR]

Recent advances in intensive rearing of astacid juvenile crayfish have greatly improved the results. This challenges the current application possibilities of the studies performed previously, and new research on density is required. A 100-day experiment was carried out under controlled conditions to evaluate density effects on survival and growth rates of juvenile crayfish in optimal conditions of feeding. Juvenile stage 2 Pacifastacus leniusculus were stocked in fibreglass tanks (1 m2, 200 l water) at 20 ± 1°C and fed a dry diet for salmonids supplemented with restricted amounts of Artemia nauplii. Stocking densities were 100, 300, 600 and 1,000 crayfish m−2. Mean survival rate was reduced significantly with increased stocking density, ranging from 86.33% (100 m−2) to 39.13% (1,000 m−2). All checks showed that at the lowest initial density (100 m−2) animals grew significantly faster those at higher densities, recording a final carapace length of 15.28 mm and weight of 1.08 g. Among the treatments of 300, 600 and 1,000 m−2 no differences were found either in carapace length or in weight throughout the experimental period, with a final mean growth of 14 mm carapace length and 0.72 g weight. The final proportion of animals with chelae autotomy rose significantly with increasing stocking density, ranging from 14.44% (100 m−2) to 41.45% (1,000 m−2). This study shows that diet is a decisive factor for stocking successfully high densities under controlled conditions and provides useful information to set adequate densities in accordance with the production objectives. [ABSTRACT FROM AUTHOR]

The acocil C. montezumae is a freshwater crayfish endemic to the Central Plateau of Mexico, but, in recent years, the natural population of this species has diminished considerably. In this work was investigated growth performance and feeding of this crayfish reared at high densities. A random block experimental design with two repetitions and three treatments (77, 154 and 231 crayfish/m2) was carried out. Organisms were fed every third day with 15% of their total biomass of shrimp commercial food with 25% of crude protein, and individual food consumption (IFC) was calculated. Significant differences (ANOVA, P < 0.05) were detected in final weight, absolute increase, relative rate of increase, instantaneous rate of increase, yield and survival rate between the densities, with those reared at a density of 77 organisms/m2 reaching the largest sizes. There were no-significant differences (P > 0.05) among treatments in terms of initial weight, specific growth rate and feed conversion l rate. [ABSTRACT FROM AUTHOR]

Theoretical models of animal assessment and decision strategies have assumed animals possess accurate information about themselves. The imperfect nature of self-assessment could cause animals to make inaccurate decisions during agonistic encounters. By manipulating sensory information used in self-assessment in crayfish, Orconectes rusticus, it may be possible to alter either decision-making paradigms or outcomes associated with agonistic encounters. We examined the role of self-assessment in the agonistic behaviour of crayfish by using differing shelter sizes to alter self-assessment of size. Similar-sized crayfish were kept in tanks with small, medium, and large shelters (relative to body size) and subsequently were fought against size-matched, naive opponents in novel chambers to remove resource value as a variable. Crayfish in small shelter treatments initiated and won more fights than crayfish in other shelters. Crayfish in the small shelter treatment had shorter durations of fight when compared to crayfish with the medium and large shelters. These results are consistent with the concept that crayfish placed in smaller shelters may be self-assessing their physical size and, thus, their fighting ability, higher than crayfish in larger shelters. Based on these results, current theoretical models need to include the role of inaccurate self-assessments in agonistic decision making paradigms. [ABSTRACT FROM AUTHOR]

The presence of two male morphs in crayfishes of the family Cambaridae is well established, but the selective value of this trait is unknown. Measurements of growth following molts to Form I and Form II were used to examine the hypothesis that alternating between the two molts may serve as an adaptation allowing animals to efficiently increase overall body size. The results revealed that the change in carapace length was significantly greater in animals molting to Form II, whereas changes in chela length and width were significantly greater in animals molting to Form I. These differences allow animals to maximally increase body length when molting to Form II and maximally increase chela size when molting to Form I. [ABSTRACT FROM AUTHOR]

1. Species invasions are a leading threat to native species and ecosystems. How populations of native species respond to the presence of invasive species will ultimately determine their long-term persistence. 2. In this study, we capitalise on a unique opportunity to compare the behaviour and growth of naïve and experienced virile crayfish ( Orconectes virilis Hagen) populations in the presence of invasive rusty crayfish ( O. rusticus Girard ). In behavioural trials, experienced O. virilis (coexisted with O. rusticus for >30 years) showed more aggressive behaviour than their naïve counterparts. Naïve O. virilis retreated from aggressive interactions with O. rusticus 38% more often than experienced O. virilis. Experienced O. virilis spent 39% more time occupying shelter than naïve O. virilis. 3. There were also differences in O. rusticus behaviour: O. rusticus spent 24% more time occupying shelter with naïve O. virilis relative to experienced O. virilis. 4. In field mesocosm experiments with O. rusticus, naïve O. virilis declined in body mass by 1% while experienced O. virilis’ body mass increased by 6%, thus highlighting the potential population-level implications of the previously observed behavioural effects. 5. Our work demonstrates significant behaviour and growth differences between naïve and experienced O. virilis in the presence of invasive O. rusticus. Whether this difference is the result of phenotypic plasticity or evolution by natural selection remains to be determined. Either way, this area of inquiry has implications for managing native populations and species in an increasingly invaded world. [ABSTRACT FROM AUTHOR]

In the mouthparts of the crayfish, we find the flagellar exopods of the symmetrical 1st, 2nd, and 3rd maxillipeds, which do not participate in food processing but occasionally generate water currents by their repetitive beating. Earlier, we have observed and filmed the flagellar movements in freely behaving Procambarus cubensis reared in the laboratory, and suggested that these movements were an overt expression of the excited state of the crayfish. Recently, we used a high-speed scan camera (100-240 fps) to observe and document the flagellar movements in the tethered crayfish. Beating of all six flagella occurs with the same frequency (8.3-8.4 Hz). There is, however, an obvious phase shift between various ipsilateral and bilaterally symmetrical flagella. All right and left flagella can beat simultaneously, or only one side can be active. Each flagellum can stop for a short time, which, however, has no influence on the beating of the other flagella. Flagellar movements seen in slowly displayed video-movies are complex and variable in their trajectories, and each flagellum is moving in its own manner. It is suggested that each flagellum has its own central pattern generator, and that activation of all ipsilateral flagella concurrently is established by common higher commands. [ABSTRACT FROM AUTHOR]

The differentiation of the female reproductive system from a macroscopic and microscopic point of view was studied in Cherax quadricarinatus. For this characterization, 184 females were dissected and processed for the histological analysis. From the differentiation of the ovary up to its maturity, three ovarian morphotypes could be distinguished macroscopically: parallel strands without any contact between them, an H-shaped ovary, and a Y-shaped ovary. These morphotypes were compared within the Astacida. Four ovarian developmental stages were recognized based on ovary color, and the histological structure and relative proportion of cellular types. The post-spawning ovary was also characterized. The components of the female reproductive system sheath were described and its modifications in the ovary and oviducts were determined and compared. Theoretical aspects of the study of sexual differentiation in C. quadricarinatus were discussed within a phylogenetic framework. [ABSTRACT FROM AUTHOR]

A new crayfish, Orconectes (Gremicambarus) quinebaugensis, is described from southern New England. This species is similar in morphology to its sister species, O. (G.) virilis (Hagen), which also occurs in New England. Orconectes quinebaugensis is found in small streams with rocky or gravel substrate, with or without O. virilis or other crayfish species. Orconectes quinebaugensis differs from other members of the O. virilis species complex in the morphology of the first pleopods of adult males; in O. quinebaugensis, both rami of the first pleopod are clearly and equally recurved, and the central projection comprises 30.2-34.0% of the total length of the pleopod. In addition, it can be distinguished from all known members of the complex by the shape of the dactyl of the chelipeds. [ABSTRACT FROM AUTHOR]

Abstract: Two 100-day experiments were carried out under controlled conditions to evaluate effects of different dietary supplements on survival and growth of juvenile Pacifastacus leniusculus from the onset of exogenous feeding (stage 2). In the first experiment, a dry diet for salmonids was supplemented with six levels of freshly hatched Artemia nauplii, starting at 50, 100, 300, 500, 1000 nauplii per crayfish per day increased by 15% every 20 days, and nauplii in excess. Survival did not show significant differences, ranging from 75 to 90%. Crayfish receiving nauplii in excess had significantly higher carapace length (16.63 mm) and weight (1238.43 mg) than the other treatment groups. No significant differences were observed among the treatment groups starting at 300, 500 and 1000 nauplii per crayfish per day, averaging 15.18 mm carapace length and 975.60 mg weight. Considering costs and these results, an initial amount of 300–500 nauplii per crayfish per day increased by 15% every 20 days could be a reasonable option during the first 100 days of rearing. In a second experiment, partial substitution (50%) of nauplii with two commercial Artemia replacements was tried as supplement to the dry diet alone. Treatments were 500 nauplii per crayfish per day, 250 nauplii+250 Artemac and 250 nauplii+250 Proton, increased by 15% every 20 days. During the trial (at days 20, 40, 60 and 80) no significant differences were found, either in survival or in growth. At the end of the experiment, similar survival (approximately 80%) and growth (approximately 14.50 mm and 850 mg) were obtained with both Artemia replacements and with Artemia only. Results showed that these replacements can be used from the onset of exogenous feeding. [Copyright &y& Elsevier]

Asymmetry in traits of sexual relevance may impair copulation behaviour and sexual performance of males, ultimately resulting in a fitness cost. Freshwater crayfish males use chelae, a sexually selected trait, to secure and position the female prior to and during mating. Thus, a relatively large chelae asymmetry, resulting from accidental loss and regeneration of one cheliped after autotomy, could have great consequences for male sexual behaviour. We studied copulatory behaviour and sperm expenditure of males paired to a mated female in Austropotamobius italicus, a freshwater crayfish species where both male and female mate multiply and where last-mating males are able to actively remove previously deposited sperm. We aimed at assessing whether male sperm removal and expenditure varied according to sperm allocated by first-mating males, and according to copulation behaviour and phenotypic traits (carapace length, chelae length and relative chelae asymmetry) of second-mating males. Second-mating males did not adjust their ejaculate size in relation to first-mating male ejaculate, nor to the first-mating male’s sperm removed. Moreover, the amount of sperm removed by second-mating males increased with increasing first-mating males ejaculate size, and first-mating male sperm remaining after removal did not correlate with the original first-mating male ejaculate size. Interestingly, the amount of sperm removed by second-mating males decreased with increasing relative chelae asymmetry, while increasing with male body size. However, second-mating (but not first-mating) asymmetric-clawed males produced larger ejaculates than symmetric-clawed ones. Importantly, the proportion of second-mating male sperm remaining after the two matings did not vary with relative chelae asymmetry nor with body size of second-mating males. Thus, small, asymmetric-clawed crayfish males appear to adopt sperm allocation tactics that allow them to fully compensate for their inferior sperm removal ability. [ABSTRACT FROM AUTHOR]

A new species of crayfish, Orconectes taylori, is described from tributaries of the North Fork Obion River in western Tennessee (common name: Crescent Crayfish). It occurs in small to medium size sandy bottom streams, and is found in leaf litter and woody debris along the banks. It belongs to the subgenus Trisellescens Bouchard & Bouchard, 1995 and can be distinguished from other species in the group by a combination of the length and curvature of the central projection of the form I gonopod, carina on the rostrum, appressed tubercles on the margin of the palm of the chela, and width of the areola. In the course of this study, a new drainage record was obtained for Orconectes pagei Taylor & Sabaj, 1997 formerly thought to occur only in tributaries of the Tennessee River in western Tennessee [ABSTRACT FROM AUTHOR]

Procambarus pentastylus, a new crayfish of the subgenus Pennides, is described from the Calcasieu River drainage of southwestern Louisiana. The species formerly was confused with Procambarus dupratzi Penn, 1953 but differs in several details of the form I male pleopod, including shorter terminal elements and the presence of a large adventitious process (here termed the pentastyle) mesial to the central projection. Procambarus dupratzi as here restricted is known only from the Sabine, Neches, and Trinity River drainages in Louisiana and Texas. A key to form I males of Pennides species known from west of the Mississippi River is presented. [ABSTRACT FROM AUTHOR]

Baited modified minnow traps are often used to collect rusty crayfish (Orconectes rusticus), an invasive species in many areas of North America. However, the use of baited traps as a collection gear for decapods has received considerable scrutiny. We designed a tank-experiment to determine if captured rusty crayfish exclude uncaptured rusty crayfish from baited traps. We found that significantly more crayfish were captured in traps where captured crayfish were immediately removed (experimental tanks) than in traps where crayfish were not immediately removed (control tanks). in addition, more small crayfish were captured in the experimental tanks. These results are consistent with a hypothesis that large and aggressive previously captured rusty crayfish exclude other, generally smaller, rusty crayfish from the trap. [ABSTRACT FROM AUTHOR]

In many species, social interactions play a key role in deciding resource allocation. Aggression is one mechanism by which crayfish become dominant, which, in turn, enables them to acquire higher-quality resources. In crayfish, hierarchies and dominance structures are formed by dyadic interactions. In natural habitats, crayfish have agonistic interactions that often take place with other crayfish in the vicinity. There is a possibility for observers to gain information about potential future opponents. We were interested in examining the impact of observing agonistic interactions on the social behaviour of a bystander crayfish. Bystanders were visually exposed to one of four treatments followed by an agonistic interaction with a naïve individual. Treatments consisted of: (1) two size-matched crayfish fighting (fight treatment); (2) two size-matched crayfish not fighting (visual control); (3) an empty fight arena with a retractable wall (motion control); or (4) an empty tank with no retractable wall (handling control). The second interaction, where the bystander crayfish was fought against a naïve size-matched individual, or tester crayfish, was analysed by a person, blind to treatment, for initiation, winner–loser and temporal dynamics of escalation. Our results indicate that bystander crayfish exposed to the fight treatment lost significantly more often to tester crayfish than bystander crayfish subjected to control treatments. In addition, there were changes in the fight dynamics for the bystander crayfish. These results show that observations of interactions by a third crayfish have implications for hierarchies and social behaviour in natural settings. [Copyright &y& Elsevier]

Nine species, including two new species of decapod crustaceans, are described from the Paleocene Rancho Nuevo Formation, collected from two localities of the Parras Basin, southeast Coahuila state, Mexico. The astacid Enoploclytia gardnerae (Rathbun, 1935) is represented by a pair of large chelae and one cephalothorax. An incomplete nephropid carapace is identified as Enoploclytia sp. Partial specimens of a callianassid and a pagurid are described. One partial carapace representing Linuparus wilcoxensis Rathbun, 1935 is described. A new raninid, Macroacaena venturai new species extends the genus into Mexico. Paraverrucoides alahamensis (Rathbun, 1935) is the most abundant species, followed by Tehuacana tehuacana Stenzel, 1944 and Viapinnixa perrilliatae new species. Taxonomic affinities of this assemblage confirm influence of the Mississippi Embayment, particularly from Paleocene stratigraphic units of Texas and Alabama. [ABSTRACT FROM AUTHOR]

The freshwater crayfishes are distributed across all but the Indian and Antarctic continents with centers of diversity in the southeastern Appalachian Mountains in the Northern Hemisphere and in south–east Australia in the Southern Hemisphere. There are currently over 640 described species of freshwater crayfishes with an average of 5–10 species still being described each year. Freshwater crayfishes can serve as keystone species in aquatic habitats, but a few species are also significantly invasive and can cause impressive damage to the fragile freshwater habitat. Crayfishes inhabit caves, burrows, streams, lakes and strong burrowers can even be found in terrestrial habitats where they have burrowed to the water table or where rainfall is sufficiently abundant to provide the needed moisture. The freshwater crayfishes, like the habitats in which they are encountered, are generally endangered to some degree and conservation efforts would do well to focus on them as key elements of the freshwater ecosystem. [ABSTRACT FROM AUTHOR]

Juvenile noble crayfish, Astacus astacus and spiny-cheek crayfish, Orconectes limosus were reared from the 2nd and the 3rd developmental stage (i.e. since the stage of independence), respectively, until the end of the growing season. The first period revealed very low survival rate of O. limosus in the communal stock (7 ± 6.2%), probably caused by predation of A. astacus. Separately reared O. limosus proved significantly higher survival rate (49 ± 9.2%) than those in the communal stock with A. astacus. The latter species also showed the highest survival rate in this case (90 ± 7.1%). This was not found to differ from the survival rate of separately reared noble crayfish (86 ± 3.1%). In general, both the significant effect of bigger size of A. astacus than that of O. limosus and higher intra-specific cannibalism of O. limosus were reflected during the first phase of rearing. Size and weight of both species were equivalent 11 weeks after hatching (8 weeks of rearing). The higher cumulative survival rate was reached in the intraspecific culture of A. astacus (90%) while low cumulative survival of both species was found in communal stock (less than 50%) in the second phase of rearing. At the end of the growing season, 19-week-old O. limosus attained a higher mean size and weight but were more variable in the group (29.3 ± 5.17 mm and 616.4 ± 412.53 mg) than A. astacus (21.2 ± 1.82 mm and 229.9 ± 59.45 mg). Single and communal stock did not differ. Growth of O. limosus was much faster than that of A. astacus. [ABSTRACT FROM AUTHOR]

The American Fisheries Society Endangered Species Committee herein provides a list of all crayfishes (families Astacidae and Cambaridae) in the United States and Canada that includes common names; state and provincial distributions; a comprehensive review of the conservation status of all taxa; and references on biology, conservation, and distribution. The list includes 363 native crayfishes, of which 2 (< 1%) taxa are listed as Endangered, Possibly Extinct, 66 (18.2%) are Endangered, 52 (14.3%) are Threatened, 54 (14.9%) are Vulnerable, and 189 (52.1%) are Currently Stable. Limited natural range continues to be the primary factor responsible for the noted imperilment of crayfishes; other threats include the introduction of nonindigenous crayfishes and habitat alteration. While progress has been made in recognizing the plight of crayfishes, much work is still needed. [ABSTRACT FROM AUTHOR]

Olfactory cues are among the sensory inputs that crayfish use in establishing dominance hierarchies. Throughout their lives, new neurons are continuously added into brain cell clusters 9 and 10, which contain somata of olfactory local and projection interneurons, respectively. Using markers for DNA synthesis (bromodeoxyuridine) and mitosis (phospho-histone-3), we tested juvenile crayfish (Procambarus clarkii) to examine effects of pairwise social experience on proliferation and survival of cells in these brain regions. Proliferating and mitotic cells appeared within restricted neurogenic areas in both clusters and in `tails' extending from them. These tails, embedded in tubulin-positive strands, are linked by a patch of cells. Neither cell proliferation nor mitotic activity was affected by social dominance. Cell survival of neuronal precursors was affected by dominance: compared to dominants, subordinates had fewer newborn cells surviving in cluster 9 after 14 days of social experience. Social experience also affected body growth rate, but the effect of social experience on neurogenesis remained when differences in body growth rate were statistically controlled. We conclude that social domination enhances survival of new olfactory interneuronal precursors compared to social subordination but not compared to social isolation. [ABSTRACT FROM AUTHOR]

Our study examined the effect of dominance on feeding, mating behaviour, and shelter use in the crayfish, Orconectes rusticus. In three different experiments, dominance and resource use were recorded in male populations, mixed-sex populations, and when crayfish were alone. Crayfish established dominance status in populations or through status conditioning and had access to variable resources (food, mates, and/or shelters) in each experiment. Subsequent resource use was quantified and compared to dominance rank. Our results did not match conventional predictions that dominance would confer increased access to resources. Top ranked dominant crayfish occupied shelter significantly less than lower ranks. This differential shelter use may be due to dominant motivation to reinforce status, as dominants also participated in the most agonistic interactions. When dominant crayfish had access to resources in the absence of conspecifics, dominant crayfish occupied shelter significantly more than subordinate and naïve crayfish. This result illustrates that present social context has a significant impact on behavioural decisions in crayfish. Social history and social context interact to determine shelter occupancy in this case. Feeding and mating was unaffected by social status in our populations. This is a surprising result given current views on the role of dominance and aggression in many animal systems. The consequences of dominance for resource use in crayfish do not follow our current understanding of resource holding potential. We hypothesize that these consequences vary due to changing behavioural motivations in different social contexts. Future studies should examine under which conditions dominance may impact feeding and mating and whether differential resource use results in differential reproductive success. [ABSTRACT FROM AUTHOR]

Abstract: In 1975, a recent member of a large group of Crustacea Decapoda was described as Neoglyphea inopinata Forest & de Saint Laurent, until now only known as fossils and presumed extinct since the Eocene. The only known specimen had been collected in the Philippine waters, in 1908, at a depth of 200 m. During the next years, three oceanographical expeditions gave more adult specimens, allowing complete study of the species. From its morphology, it appeared that the status attributed to glypheids in the past in the classification of Decapoda Crustacea was quite erroneous. This group, until then considered as related to Palinurids (rock lobsters) was in fact much closer to Astacids (lobster, crayfish, etc.). In 1982, N. inopinata was recorded from the other side of Equator, from the Timor Sea. In October 2005, a second living species of glypheid was discovered southwest of New Caledonia. It was named Neoglyphea neocaledonica B. Richer de Forges, 2006. However, important and significant differences set apart the two species, especially the ornamentation of the cephalothorax, the conformation of the cephalic part and the proportions of epistom and thoracic appendages, being much more robust. It seems justified to establish, for the more recently described species, a new genus, Laurentaeglyphea, much closer to fossil forms. To cite this article: J. Forest, C. R. Biologies 329 (2006). [Copyright &y& Elsevier]

The phylogenetic position of the four East Asian freshwater crayfish species of the genus Cambaroides is not settled. Morphological phylogenetic analyses suggest close affinities of Cambaroides with North American Cambaridae. This view is based mainly on characters of the male and female reproductive organs. In contrast, the only molecular phylogenetic analysis so far available leaves the phylogenetic position of Cambaroides unresolved. The question of whether Cambaroides is monophyletic or paraphyletic has so far been neither addressed morphologically nor with molecular data sets. Here we present the first comprehensive phylogenetic analysis of all four currently described species of Cambaroides in the framework of Northern Hemisphere freshwater crayfish (Astacoidea) relationships based on partial sequences of two mitochondrial genes ( CO1 and 12S rRNA). Despite some evidence in favour of a monophyletic Cambaroides more data is needed to resolve this question. Our analyses suggest a close relationship of the North American Cambaridae and the European Astacidae, leaving the Asian Cambaroides basal to them. If these results hold true the similar reproductive organs of Cambaroides and American Cambaridae must be either homoplastic or ancestral for Northern Hemisphere Astacoidea. [ABSTRACT FROM AUTHOR]

Chemical signals in aquatic systems are used to communicate social status and consequently alter aggressive behaviour. In addition, they may also function to influence the status roles of potential opponents or in part to predetermine the outcome of agonistic interactions between opponents. Here we examined whether exposure to social odours, in the absence of other sensory contact with a ‘sender’, alters subsequent agonistic behaviour in crayfish. Odour-receiver crayfish were exposed to one of four different odours from a ‘sender’ crayfish: odours from dominant (winner), subordinate (loser), or naïve crayfish, or water from a tank that did not contain a crayfish (no social odour). ‘Receiver’ crayfish were exposed to one of the aforementioned odours on five consecutive days. After this extended exposure, the ‘receiver’ crayfish was allowed to interact with an effect-evaluator crayfish that had been isolated during the 5-day exposure period. ‘Receiver’ crayfish that were exposed to dominant (winner) odours behaved analogous to a subordinate role in that these animals lost the majority of their fights, but they also fought more intensely compared to the other treatments. Conversely, when crayfish were exposed to subordinate (loser) odours, their agonistic interactions were less intense and they subsequently won more encounters compared to the other treatments. These results may suggest that the receivers of the dominant odours had exhausted their chemical signal reserves by responding to the signal and therefore were obliged to increase their levels of visual/tactile responses. Because their chemical reserves were no longer sufficient to reinforce the visual displays corresponding to increased fight intensity, these animals tended to lose fights. In contrast, the receivers of the subordinate odours probably had sufficient chemical reserves to communicate chemically during agonistic encounters, and consequently, won more fights. [Copyright &y& Elsevier]

Third-instar young-of-the-year (YOY) and juvenile Procambarus acutus acutus and P. clarkii stocked in aquaria, rice forage microcosms and a culture pond were evaluated in intraspecific- and interspecific-competitive settings. Procambarus acutus acutus YOY, which were larger than P. clarkii YOY at stocking, grew and survived at significantly greater rates over fall-, winter- and spring-temperature courses in aquaria. Juvenile P. a. acutus starting an aquarium experiment with a mean total length (TL) size advantage survived at a significantly greater rate than P. clarkii juveniles. Growth rate of similar-sized stocked P. a. acutus juvenile was significantly faster than that of P. clarkii juveniles in the same microcosms. Survival of juvenile P. clarkii in the microcosms with P. a. acutus was significantly less than when stocked alone. Estimated survival of 2200 P. a. acutus and 2200 P. clarkii YOY in a culture pond over a 174-day grow-out period was 84% and 57% respectively. Growth rate of these YOY P. a. acutus and P. clarkii was 0.48 and 0.40 mm TL day−1. The body-size advantage at hatching and through the faster growth of P. a. acutus was important in defining competitive interaction with P. clarkii. [ABSTRACT FROM AUTHOR]

Native European freshwater crayfish (Astacida, Decapoda) are under severe pressure from habitat alteration, the introduction of nonindigenous species, and epizootic disease. Crayfish plague, an acute disease of freshwater crayfish caused by the fungus-like agent Aphanomyces astaci, was introduced into Europe in the mid-nineteenth century and is responsible for ongoing widespread epizootic mortality in native European populations. We reviewed recent developments and current practices in the field of crayfish pathology. The severity of crayfish plague has resulted in an overemphasis on it. Diagnostic methods for detecting fungi and fungal-like agents, and sometimes culturing them, are frequently the sole techniques used to investigate disease outbreaks in Eumpean freshwater crayfish. Consequently, the causes of a significant proportion of outbreaks are undetermined. Pathogen groups well known for causing disease in other crustaceans, such as viruses and rickettsia-like organisms, are poorly understood or unknown in European freshwater crayfish. Moreover, the pathogenic significance of some long-known pathogens of Eumpean freshwater crayfish remains obscure. For effective management of this culturally significant and threatened resource, there is an urgent need for researchers, diagnosticians, and resource managers to address the issue of disease in European freshwater crayfish from a broader perspective than has been applied previously. [ABSTRACT FROM AUTHOR]

The article presents information about crayfish species. Astacus leptodactylus and Astacus pachypus live in waters of up to 14 ppt salinity in the Caspian Sea. A. leptodactylus, the only crayfish native to Turkish waters, is known from estuarine environments. Various studies have been conducted on determining the salinity tolerance of a number of crayfish species through survival and growth trials. Some researchers state that their ability to colonize the estuarine environment may be restricted to areas of low salinity due to the adverse effects of sea water on egg development and hatching. Hence, consideration of a brackish-water environment may be more realistic.

Juvenile (mean weight 8.1 g) Australian red claw crayfish, Cherax quadricarinatus, were stocked in July at three rates of 12,000/ha, 18,000/ha, and 24,000/ha into two, 0.02-ha earthen ponds in a cool temperature region of the United States (Kentucky) and grown for 70 days. Red claw were fed a pelleted marine shrimp diet twice daily. Ponds had continual aeration provided. Dissolved oxygen and temperature were measured twice daily (0900 and 1530 hours); total ammonia nitrogen (TAN), nitrite, and alkalinity were measured twice weekly, and pH was measured daily. At harvest, there were no significant (P > 0.05) differences in final individual weight, percentage weight gain, specific growth rate, feed conversion ratio, percentage survival, yield, and economic return among all treatments and averaged 58.4 g, 805%, 3.04%/ day, 7.47, 42.7%, 461 kg/ha, and -$2659/ha, respectively. There were no significant (P > 0.05) differences in the percentage of males and females harvested from the ponds among any stocking rate with males comprising 48.2% and females comprising 51.8%. Final individual weight of males and females was not significantly (P > 0.05) different among all treatments. These data indicate that there is no advantage to stocking red claw at rates below 24,000/ha in terms of growth, survival, yield, and economic return and that red claw can grow to marketable size in a cooler temperate region of the United States with a short (<110 days) growing season by stocking a larger-size (8 g) red claw. [ABSTRACT FROM PUBLISHER]

The complete mitochondrial DNA sequence was determined for the Australian freshwater crayfish Cherax destructor (Crustacea: Decapoda: Parastacidae). The 15,895-bp genome is circular with the same gene composition as that found in other metazoans. However, we report a novel gene arrangement with respect to the putative arthropod ancestral gene order and all other arthropod mitochondrial genomes sequenced to date. It is apparent that 11 genes have been translocated (ND1, ND4, ND4L, Cyt b, srRNA, and tRNAs Ser(UGA), Leu(CUN), Ile, Cys, Pro, and Val), two of which have also undergone inversions (tRNAs Pro and Val). The ‘duplication/random loss’ mechanism is a plausible model for the observed translocations, while ‘intramitochondrial recombination’ may account for the gene inversions. In addition, the arrangement of rRNA genes is incompatible with current mitochondrial transcription models, and suggests that a different transcription mechanism may operate in C. destructor. [Copyright &y& Elsevier]